Add method to DeleteCommitmentController and Observer

Signed-off-by: Hui Zheng <fengyimzy@gmail.com>
Merge branch 'feature-deleteCommetController' of github.com:Tommzy/wpi-suite into feature-deleteCommetController
Modified the result text showed in the DeletCommitmentObserver

Signed-off-by: Hui Zheng <fengyimzy@gmail.com>